doc: Update security policy

Author: jcdcdev

SECURITY.md

@@ -9,8 +9,12 @@ The following table outlines the versions of the project that are currently supp
 
 | Package Version                                                                            | Umbraco Version | Security Phase Start | End of Life |
 | ---------------------------------------------------------------------------------- | --------------- | -------------------- | ----------- |
-| [15.x](https://github.com/jcdcdev/Umbraco.Community.SimpleTrees/tree/v15) | 15 | 2025-08-14 | 2025-11-14 |
 | [16.x](https://github.com/jcdcdev/Umbraco.Community.SimpleTrees/tree/v16) | 16 | 2026-03-12 | 2026-06-12 |
+## Unsupported Versions
+
+| Package Version                                                               |  Umbraco Version  | End of Life |
+| ---------------------------------------------------------------------------------- | ---------------  | ----------- |
+| [15.x](https://github.com/jcdcdev/Umbraco.Community.SimpleTrees/tree/v15) | 15 | 2025-11-14 |
 
 
 ## Future Support